I found out the answer. The type of backup can be seen on backup storage tab if you select a file. Now the question is, the original file was 137MB and was taken full. After an hour did block-level of the PST which was 151MB and the block-level was 8.2MB. Then a incremental was taken and the backup was 109MB. The question is, if you try to restore the latest version the last full + block -level would be in the restore process? Please advise the photo.

Just the latest full would be restored.

The block level backup where it should be used in this case? If someone has some block level and then decided to do incrementals only what would happened to block levels?

Your screenshot shows 3 backups: A full, followed by a Block-Level, and then another full. To restore the latest version, all you need to do is restore the latest full.

Thanks for your answer, however you did not replied to my question. What would happened to block levels if I decided to take only ''incrementals" in which them are shown in storage tab as FULL

I do not understand the question. If you only performed full backups and had no block-level backups, then you effectively have many full backups of the same file. Block-level backups belong to a specific full backup. They will only be removed from backup storage according to your retention settings.

Where is retention setting for block level backups.

There isn't. Retention is based on versions and / or time and removal of files (full or block-level) are handled automatically based on those retention settings. There is no point in keeping a block-level if you're removing the full that it's related to; hence, the automatic handling of all file backup types based on retention settings.