Formation of Fossils

The first fossil is an example of Replaced Remains because you mainly see bones there and the bones decayed and were replaced with rock-forming minerals.
The second fossil is an example of Original Remains because the whole insect there is preserved entirely in the amber, which use to be sticky sap that trapped the insect.

Relative Dating and Strata

3 is the youngest because of cross-cutting relationship. After that 1 is younger than 6 because of superposition. Then 2 is after 6 because it doesn't reach the top but also because of cross-cutting relationship. Lastly, 5 is younger than 4 because of superposition. So the order from youngest to oldest is 3, 1, 6, 2, 5, and then 4.