According to what I have read in the press, I have serious doubts that Russians will let PAF have the RD93M engines. India will surely object and Russians wouldn't want to displease India.
Here's the thing...there are no press reports about RD-93M (i.e. upgraded RD-93), this was solely reported by Usman Ansari or at best, is a PakDef thing only. Yes the Indians have an issue with RD-93 being sold to PAF, but time and time and time and time and time and time again the PAF said the engines are not a problem and the Russians agreed to sell. Basically what is happening is that the Indians are beating a dead horse (engine rumours) in order to scuttle JF-17's export hopes...but that too will fail once WS-13 is fully available.
Russians offering us MIG-35?....I dont think so we need to be that positive....even if they do, I suspect PAF will not respond positively as we already have a handsome (infact more than handsome) numbers of MRF which Mig-35 is....if PAF goes with expected ToPT for FC-20, I dont think PAF would like to take the headache of building more infrastructure for a new project i.e. Mig-35. Engine Manufacturing, well i don't know whether Russians have offered such to any other countries (not even India and China) so I wont place my hopes on this option as well....and lastly S-400, No to that too as Russians are hesitant to provide this prime system to even China...so where does Pakistan Stand, I leave it upto you
Firstly, an export variant of the S-400 is being developed but won't be available for at least another few years. Its a matter of actually having the money and illustrating the fact that other viable options are available. Were you around to see the kind of beating I'd get in 2003-2004 when I said PAF could get Block-52+? You decide.
Secondly, the MiG-35 (if offered) would be in contention to the FC-20: Simply put, FC-20 is a bigger fish than even the F-16s and depending on the circumstances, PAF can acquire up to 150 FC-20. The Russians aren't going to let such a lucrative possibility slide that easily, especially if India plans to reduce its reliance on the Russians by going Western for MMRCA. The technical merits are on the table...engine commonality with JF-17; solid high performance fighter when appropriately equipped (not an issue for PAF); and fleet potential 120~150 would include a local manufacturing offer. In fact, a bunch of Indians once reported that PAF officials were talking to the MiG-delegate about MiG-35 at some air show, and were noted to have shown a lot of keen interest.
As for engines, the Russians won't leak everything, but when an air force operates 300 to 400 fighters using the same engine, the client state can certainly make a decisive case. Even if the Russians released up to a limited point, that is still a gain and form of contribution to the indigenous R&D - i.e. something to work with. At the end of the day, its about making a concrete case and coming up with the money, if accomplished, the Russians aren't that much of a problem.