proof of stake concept and implementation confusion

i’m currently studying proof of stake concept in cryptocurrency in preparation of building it soon, but i still have some doubts about my understanding of the concept itself, and i have a lot of questions about it.

IF i set the max supply of 21 millions coins, question is :

  1. do i have to premine all the coins (21 millions of them) and put it in the programs’s wallet? or just let it not mined at first, and release the coins when the forger have solved a block?

  2. do i have to build an offline wallet (windows, mac, linux os) or is an online web wallet will be enough for POS staking?

  3. about the POS itself, lets say for example there are 100 stakers, with various amount/percentage of coins staked, i understand they’re given interest lets say for example 5% a year on their staked coins, which stakers will given a block to solve the hashing problem? will it be random based on their percentage of stakes? will the comission of solving the block go to the solver (1 staker) or go to all of the stakers by percentage of their stake percentage (100 stakers).

  4. according to What is proof-of-stake? it was said that someone possessing 1% of the total stakes “mine” 1% of the total blocks, it gets confusing here, if example 1 block contains 100 transaction, so this 1% stakers will be solving hash of 1 transaction? is this correct?