Regex: can contain the specified characters, but must contain a letter - how?

Question

Regular Expressions

Folks, please help me compose a regular expression:
1) the string starts with a letter or number
2) it can contain a-z0-9_.
3) must contain at least 1 letter az
This expression: (^([a-z0-9]){1}[a-z0-9_.?]+)$
includes a string of numbers only, which contradicts condition 3.
https: //regex101.com/r/FylFY1/469

Answer 1

^(?=.*[a-z])[\da-z][\w.]+$

Answer 2

^(?:[0-9][a-z0-9_.]*)?[a-z][a-z0-9_.]*$