When creating a LAG, what VLAN conditions should be satisfied? There are two interfaces which are to be added in a LAG. The attributes which should be same are speeds and MTU values. What about physical interfaces which are in different VLANs. For example, Port 1 is in VLAN50 and Port 2 is in VLAN100. Can both be allowed to be a part of a LAG Interface ? Also, can tagged and untagged both be allowed to be a part of single LAG interface?

Aggregated physical links are logically just a single link. Accordingly, you configure VLANs, STP, frame size, etc on the logical link, not the physical ones. All physical links in a LAG trunk are required to run at the same speed. Physical interfaces normally lose any prior configuration when aggregated.

If you want to keep VLANs separate with multiple links you can't simply aggregate them. Using multiple spanning tree protocol (MSTP), it's possible to configure multiple MSTP instances with grouped VLANs, so you can utilize both links with separate VLANs. Redundancy is still provided since the MSTP instances reconverge on single link failure (with all required VLANs configured on the redundant interfaces).

And of course, you can also have multiple links with separate VLANs between two switches - note that you'd have to deactivate RSTP and MSTP unless MSTP is configured correctly for multiple instances (since RSTP and single-instance MSTP are VLAN-agnostic).