You didn't even need spare parts to build the American drones or the American aircraft like the F-14s. What you need or want is the actual copy of the aircraft. The moment you get your hands on SU-35s or 34s, you are good to go in the long run. Whether the Russians change their mind, would the Iranians really worry?
Iranian aviation industry has been playing with american planes for a long long time. They can copy them from scratch with local avionics (F-5E/F => Kowsar), modify their aerodynamics (F-5E/F => Saeghe I/II), rebuild them and upgrade them extensively (F-4E/D, F-14). Same is not true for Russian fighter planes. The reason is more political then technical. It took IRIAF years to study and bring SU-24M to operational status, and as per reports even today the fleet is having difficulty with spares. They sent entire squadrons of SU-22 and SU-25 to Syria and Iraq to probably get rid of the maintenance strain. Meanwhile we never saw any proper upgrade of the MIG-29 fleet. The radar and avionics on the MIG is ridiculously obsolete and airframes are now asking for MLU by age. We are hearing news of an MLU center being set up in mehrabad but I personally believe a proper Russian hand must be involved there. Russians have this history of not letting their clients touch their systems indigenously. You need to upgrade any Russian plane, you need to contact the Russian front companies that usually have offices in eastern European countries (Serbia, Belurus, previously in Ukraine). No country in the entire world has ever pulled an extensive upgradation on any fourth gen russian fighter/attack jet without sending back money to Russia through whatever way. Compare that to our extensive upgradation on F-4E/D that brought the plane to JH-7 like strike capability. Same case is with F-14AM which saw the partial airframe rebuilt, with datalinking, massive radar upgradation with new long-range BVR missiles installations. Iranians probably know more about F-5E/F then Northrop itself ever did.
Then there is unreliability in supplies too. in 1990s we ordered 72 x MIG-29 and 30 MIG-31. We only got 24 MIG-29 9.12 (Russian sources claim they delivered 40 airframes). The 48 MIG-29 and 30 MIG-31 became victims of Yeltsin's fear of American sanctions. What happens if Iran gets 50 SU-35S and then Russians pull the plug on spare parts supply? the fleet will become useless. Yes Iran can start establishing up a SU-35S reverse engineering setup that may get functional in next 10 years. But even that will require a manpower of some 10000 managers/workers/technicians of different types and Billions of USD. Project will suck life out of Iranian aviation industry.
Instead what Iran can do is focus on its domestic fighter program. We have one platform that is called Kowsar (from scratch + parts repository-based building of F-5E/F) which in its weight category is probably the most advanced fighter jet in the world. It is not easy to mess with a 1m2 RCS bearing aircraft that can search/ track an F-16 size adversary at some 110/93 KM distance, can jam your ARH missiles, datalink with UCAV's+other fighters+Airdefence Radars, can take out ground targets with a Ballistic computer like SU-24MK. All the while, the same airframe is known to have beaten F-15C, F-14A in dogfights. We believe its production will conclude by 2026 and then there will be a newer, better generation that may have technologies like AESA radars, HOTAS, Single Crystal Turbofan etc. So we can have shiny new 50 x SU-35S for 6 Billion USD to procure and operationalize and then spend 10-12 more years trying to understand it to reverse engineer while making Moscow furious
OR
for the same amount of money we can build 400 Kowsar-I/II/III while simply asking Russia to MLU the MIG fleet and if they can, provide more airframes (may be ~50). An interception wing made of all datalinked 50 x F-14 + 70-80 MIG-29 + Hundreds of Kowsar I/II is a good force, atleast to deal with regional adversaries in conjunction with layered LORADS and SHORADS. While 100+ x F-4/E/D+SU-24MK2 and 300+ MALE UCAVs can take the attack role along with our very strong Missile forces. I feel Tehran understood this game much earlier.
There are currently no laser enrichment facilities in Iran. I wonder what officially known facility you are referring to.
In fact, Iran's experiments with laser enrichment date back to late 1990s, done covertly.
In 2002 Iran established a pilot
uranium laser enrichment plant at
Lashkar Ab'ad, and between 2002 and 2003 conducted
enrichment experiments.
https://www.nti.org/education-center/facilities/lashkar-abad/