If i want to stake DMD, pos, do i must have at least 100 coins in my wallet?
Here is no minimum limit on the number of DMD.
You can participate in POS staking even with 10 DMD.
But the time for search a block will be long.
Focus from income to 25% per annum.
That is, the more coins you have in one group, the faster you can find a POS block.
To date, the optimal number of coins for one group is 150 - 200 DMD.
You can also find more information after reading the questions and answers on this page
https://diamond-info.github.io/