Good day! For example there is a field where the id field does not exceed 127, but the data can be deleted and new ones added, and I'm afraid that when id reaches 127 it will no longer be added or it will start to add those values which are absent in the id field?
No. If the field is defined as TINYINT AUTOINCREMENT, then after reaching 127 attempt to add the new entry will fail. Gaps are formed when you delete records, or when unfinished transactions are not automatically filled in.