Since the word "dangerous" is considered a long adjective (of 3 or more syllables), the words "more" and "most" are used to form the comparative and superlative forms. The comparative form is more dangerous. The superlative form is most dangerous.
more dangerous most dangerous
More dangerous Most dangerous
Yes.
A secret plan to do something REALLY bad, harmful, or dangerous.
most dangerous, most cheerful
Safer Walking is safer than cycling
"More harmful" and "most harmful." We would not use the -er and -est suffixes on the -ful which is already a suffix.
Sleep is a noun and does not have a superlative. Sleepy is an adjective and the superlative is "sleepiest."
The superlative for willing would be "most willing." There is no one-word superlative.
"Studying" is not a superlative, as it is not an adjective. "Most studious" is a superlative of "studious."
"Bib" is a noun and, as such, does not have a superlative form.