Obviously when negotiations between two sides happen there is usually room for some things to change

I find it remarkable that Russia insists on Ukraine being a demilarization zone

Ukraine gave up nuclear, how well did that work for them

N Korea watched and decided they will never give up nuclear

Some things you need for sovereign security and Russia has to know Ukraine will never allow their military to be dis banded

Russia would not dis band their military so it is for Ukraine

So: Russia must not be serious but using Ukraine military as a bargaining chip

All other Russia demands could be negotiated

Will Russia allow grain crops. I think Ukraine has decided to not allow exports out of Ukraine so Ukraine must think domestic food  production will be the most Ukraine can hope for until a cease fire. Ukraine is doing some top dressing of wheat in day light hrs only

IMO Russia wants more time to destroy as much infrastructure as possible to keep Ukraine re-building instead of spending on re-build of military. Also want time to delay food production thus a weakened Ukraine and less foreign exchange from exports to buy essentials

A lot of possibilities but what do you think