mysql vs. flatfiles

I have been using flat files for a while but thought I should learn
mysql. There are two things I dont like about mysql compared to using
flatfiles. They are:

1) When creating a table why do I need to define the type of data and
length so strictly, i,e int , varchar etc? Can I make a flexible table
with data of any type and length?

2) When creating a record I am using autoincrement ID. This works
great except when I delete a record it leaves a "hole" in the table.
How can I set it up to work like a flatfile where all records shift
"up" when one is deleted?

Any good tutorials that cover this?

Thanks,

.