This would include not putting controlled substances in vape cartriges is you are entering Russia. Having a prescription apparently does not work.
Well, it doesn't work with TSA in the US either, to be honest.
Yes, lots of discussion. Basically in the unlikely event of someone checking, if you can show that you will be there for the time period (return ticket) and the amount fits the time period plus maybe some safety stock (if you have a 90 day supply, don't bring it all) and you have documentation (prescription labels) then they have no issues with you having those for personal use.
Staying for a week and bringing 6 months worth...that's a problem. If you take any pain meds, Opiates or Opioids, then document better and watch quantities. There are some drugs, stimulants mainly, that are prescribed in the US, that are illegal in Europe...and of course Cannabis related products.