The fact you compare the geopolitical climate for Iran in 1990's to today is puzzling.
Fact is Iran wasnt even a significant regional power in the 90's. It was a country recovering from a brutal war.
The Soviet Union had just dissolved and there was a fire sale on arms. They were desperate for cash. They were willing to sell to anyone.
But yet even when Iran was barely a threat, the US still put pressure on Russia and China for arms deals made with iran in the 90's.
Several people in the Iranian military are critical of the establishment for not BUYING more during the early to mid 90's when Iran had a chance to procure significant arms (subs, strategic long range bombers etc)
Compare that today and it's hard to see that Russia and China will ever engage Iran seriously in any significant offensive arms deal. China is not desperate for Cash and has other clients. US can leverage South China Sea dispute to put pressure on China.
Russia is not desperate for cash and has other clients. It will use Iran as leverage for its more important interest which is sanctions and Crimea/Ukraine situation.
Furthermore, Iran doesn't have enough cash to make any mega arms deals. So why would China and Russia put their neck out for some small arms deals?
If anyone thinks that the arms embargo is going to easily come off they are naive.
The person that's naïve is you!
In the 90's Iran had already started it's weapons industry!
And don't confuse propaganda created to sell more arms to the Saudi's as FACT'S! And even in the 90's Iran was more after Technology Transfers & Co-production then purchasing weapons because it goes against Iran's defense doctrine!
Except for limited purchases for reverse engineering in the 90's Iran concluded that for specific weapons Iran would require foreign assistance & foreign weapons like Fighter Jets, Heavy Helicopters(10+ passengers), Heavy Submarines
But the problem with those type of weapons is that after a year or two (depending on the weapon) unless your getting continued foreign assistance and parts they will be useless so Iran made a limited purchase & worked towards building parts & learning how to maintain them inside the country! So a large purchase without the ability to maintain, equip & upgrade them would have just created a large junk yard nothing more!
And it was in the 90's & Iran's experience in the 80's that Iran choose to build it's defense doctrine around weapons they can produce & maintain themselves!
Right now there is a LAW passed by the Parliament prohibiting the purchase of "Fighter Jets" unless they foreign country was to at the very least agree to co-produced inside Iran!
So this idea that Iran going around knocking on doors and desperate and waiting to buy a bunch of fighter jets is nothing but a delusion! The reality is that Iran will ONLY ARGEE to buy them if the other side agrees on Co-production & gives Iran access to the weapons system!
Now US Generals & weapons dealers can go to the UAE and hype up the UAE Air Force & rant about how they have a more powerful Air Force than Iran! BUT at the end of the day they all know that even if the UAE had 500 F-35's it's wouldn't matter because Iran can at the end of the day wipe out the entire UAE Military within hours!
Why would Iran pay $150 Million USD for a Su-30 (Gear, weapons, parts,...) when with the cost of a single fighter they can drop 150 missiles or more on an Air Base, take out the enemy's Air Force & Air Defense & then use their 70's era Air Force (that they can maintain & build weapons for) plus Iranian built UCAV to take out the rest?
And yes Iran has showed interest in Co-Producing the Su-30 but due to Iran's experience in the 80's Iran is not going to simply buy that Aircraft without having access to it's weapons systems & the permission to take the Aircraft apart and produce their own spar parts!
Instead Iran will continue to invest in building it's own Jet Powered UAV's with Air-Air capabilities to be used as crude interceptors! Especially with the proliferation of Stealth Aircraft!
It's simple today Early Warning Systems can pick up stealth aircraft but since they can't detect the altitude they can't lock on so you equip a stealth jet powered UCAV with a small RCS with an IRST & IR Weapons flying at 800kph & you send two towards that heading one flying at low altitude(1000ft) one at high(15,000-20,000ft) you can control them from the ground up to 200km away but if jammed you program them to automatically detect and take out anything that doesn't have friendly IR signature once they get to that general area
Modern IR Air-Air missiles don't require you to point the nose directly at the Aircraft making it easier for UAV's to take on this task!
The UAV may be very expensive and only good for defensive purposes over your own boarder but at the end of the day it will be far cheaper than buying and operating a bunch of Su-30's that will never have a chance against an F-22
At least with the UAV you can overwhelm them with numbers because they are far cheaper and just because YOU haven't seen such a UAV in Iran it doesn't mean it's not there!