For Opacity: In the Timeline panel, expand the Layer to reveal the Transform properties. Then, expand Transform. Opacity is the last of the five Transform properties for layers that have picture.
For more on Layer properties:
For Masks: Select the Layer and apply a Mask. There are several ways to do so, one being Layer > Mask > New Mask. After being applied, the Mask will appear under the Layer in the Timeline.
For more on Masks:
That's easy to do, but it'll be time-consuming, and there's getting around it. You'll create a mask on the video layer around the subject, and then you'll animate that Mask Path property.
And if it looks like I'm writing in Greek to you, you really need to spend a lot of quality time here:
The stuff I wrote above is covered on Day 1 of the AE 101 courses. It's really, REALLY basic.
It's not click and get what you want, it's study up, learn the interface, then work at it to make it work. Please go through at least the basics. When you want to find out more about a specific task like masking then type masking in the Search Help filed at the top right corner of AE and read through some of the resources. I've been working with AE four or five days a week for more than 20 years and I use the Search Help field at least once a week because it almost always gives me more options for solving production problems....