ubuntu-image should have told you during build that locally added snaps (easily identifyable by the xNN revisions) will not be upgraded … did it not do that ?
note though that you should really only use a modified core snap when testing submissions to the official core snap, this is nothing you should ever use in production.
Ubuntu Core is a rolling release and packages might expect features from newer core versions, things will likely break in unpredictable ways at some point (not to mention that you wont be able to fix any open security holes).
i want to clear one thing that i wont build that Ubuntu core image with prebuild snap.i am just an user,but worried about future update for locally pre-install snap .
can you please explain more in details or share any reference link for study
snaps use assertions (security certificates) to verify the publisher and the store they come from:
locally built snaps are obviously not signed by a store or by a store authirity ID so their integrity and security can not be verified by snapd … you will also not be able to set defaults or pre-defined interface connections for any application snaps that do not have a snap ID assigned by a store (which a locally built snap does not have either)