Built in. Only need sun or plug in charger ( it comes with one) to power up. 

I've used the head that comes with the tripod for various shooting situations, including lay-flat photography. 

Depends on what you mean by direct sunlight. If you mean the filter pointed directly at the sun, and you are worried about lens flare, well it wont stop that. But if you mean using it out in bright bright sunlight all around, then it works great. I'm a member of the Longview Film Club. We shoot indie short films, and use these for all of lenses and cameras. It's a must when shooting outside under almost any conditions. Makes it possible to get nice Depth of Field even on a sunny day. 

I don’t know why not. The filter pack is in probably a better environment because it is indoors. Less dust and humidity. Filters are tools. You as the photographer use the tools take your image. Just think outside the box, when taking that image. Some would say there is no “wrong” way to take a “right” image. 

hello ,you can use ie take picture of the sun, but not for the solar eclipse