How I can fix the starting country code +123 (xxxxx) for shoving error when entering +124 (xxxxx) for example?
Welcome to the community, @kozhanovadim! This post discussed previously should help you solve your issue:
You should also be able to learn more regex workarounds that have been discussed in the community here.
You should also be able to learn how to build your regex code through this support article Restricting Text Responses With Regular Expressions.