What is the IUPAC name ?
1) I would take the longest main chain as the parent name.
The parent compound is octene (go from left to right to find 8 carbons in a row).
From here, the double bond takes the lowest position (2) because it is the deviation from an alkane naming. Plus, it gives a lower position number to the alkene (as it should) to say "2-octene" than "6-octene" by starting from the other end.
Going from left to right, we then have methyl substituents on carbons 5 and 6, and ethyl substituents on carbons 3 and 4. So the final name, without using a bunch of parentheses, could be:
2) Similar idea here. The longest chain is five, so pentene is the parent compound.
Therefore, the name could be:
3,3-diethylpent-1-ene (a bit redundant)
I would go with the first one, because it is not redundant, uses the longest chain for the parent compound, and is fairly concise and unique. (You can't use t-heptylpropene, by the way. Not the same thing.)