Are you an Old Earth Creationist
Yes.
The Bible, when you come to the book of Hebrews 4, actually supports the idea of the seventh day, God's Rest Day, as
still continuing in the first century CE, during which time Paul wrote those words.
And, when you read the Genesis account,
it never says 'the seventh day ended' (as the other days did). So, if
that day is not a literal 24-hr. day, there's no reason to declare the others as being 24 hours, either. (The Hebrew word for 'day' used in Genesis 1 & 2, "yom", can refer to an undisclosed length of time. Many other Scriptures substantiate this. Willing to provide them, if you'd like.)
With regard to your other questions, suffice it to say that those creative days in Genesis
having a definite beginning and ending,
refer to separate creations, some earlier than others. The fossil record is in full accord with this description of events.
I believe there is MICROevolution, since it's certainly an observation that animals do change somewhat over time. Now, why would God program DNA with this ability to mutate (albeit on a
limited scale)?
(
Now, please, bear with me.)
Because of God's love: He created humans as life forms with the capability to live forever, to never die, living forever HERE, ON THIS EARTH.
[That's what Jesus' sacrifice is (mostly) about, getting that situation back for us humans.]
And all lifeforms gradually changing, will simply give humans
more to enjoy as they (we) live forever, never getting tired of "seeing the same old things"....all flora and fauna will constantly be evolving into new species,
on Earth.
Psalms 115:16; Isaiah 45:18; Isaiah 11:6-9. (You won't hear about this in church. I never did.)
Take care.