2) You wallet should have 100 UTXOs (unspent transaction outputs, AKA unspent incoming transactions) or more.  This is because every time you stake or send an amount, that amount cannot be staked or spent for 101 blocks, while it is maturing (being staked). You can see the number of UTXOs that you have in the Coin Control dialog. Doesn't matter how many addresses or wallets they are split into. One single address can hold these 100 UTXOs.
if your balance is lower than 500 BTC2, You can get a close enough result without that much effort by splitting your balance into stacks of 5 - 50 BTC2. For example 150 BTC2 can just be split into 5 pieces and you'd be unlikely to notice the difference in efficiency of that versus splitting it in 100 parts. You can do the splitting by sending BTC2 to yourself.