CW-POV and Tense

So, the next chapter we read in the LeGuin book was bout point of view and tense.
A lot of people kind of shift the tense around in their writing. Don't do that (Unless you have a very good reason). Same with POV (except for a very good reason). You need to keep the same POV throughout. I'll summarize the main points of the chapter.
You got the first person - the "I" story.
Then second person, "you," is probably not advisable for most writing.
Third person, "he, she, it," ex is the most common.
Then you got the limited 3rd. That's where you have a main character. I'll use Harry Potter. You follow whatever Harry does and you know only what he knows, sees, hears, ex. That's a pretty common way to write.
(And you can have an all-seeing 3rd person POV, or a part seeing 3r POV, ex)
And tenses. Most things are written in past tense. You've probably noticed that. At least in stories. It can be different for essays and such.
Here's the exercise (just a page long). It's about an old woman who's doing something, and then remembers something that happened a long time ago. You're gonna switch back and forth between her as an old lady and her memory.
First, you choose either 1st or 3rd person.
Then you choose a tense:
Both can be in past tense
One can be in past one can be in present,
Or all can be in present.

You finished writing it? Good.
Because you're going to write it again . This time choose the other POV, and a different tense. Don't just copy and past on the computer. Rewrite it.