For the Maiar exchange and in particular the EGLD/MEX liquidity pool, Is that true that extra mex will be given to compensate for impermanent losses ?

No, you will not earn any extra MEX if you suffer impermanent loss while providing liquidity. The mex you earn from your liquidity pool tokens via farming already have possible impermanent loss factored into their issuance rate. Thats why EGLDMEX LPs earn more mex when farmed then others pairs or MEX on its own. EGLDMEX LPs has a higher risk of IL.

No

Yes, because you can put the EGLDMEX LP tokens to farm