thank you very much! that's what I need! 

We don't take new tasks now. But you can find plugin https://www.google.com/search?q=alphabet+archive+WordPress

can you help customize deal grid, so I can choose only to show posts which title starts with a specific letter? For example, only show posts start with A, or B, etc. 

How much? Thank you in advance!

no, but you can use include="11,22,33" etc to add special stores to grid

Can deal grid show only posts start with a certain alphabet?