onto your backs [and set out on the long rocky trail that led homeward]
A good sentence using happily is: Sam happily performed on the stage at her school.
Sure, you can start a sentence with a prepositional phrase, such as:On the table I saw a large book.You can, but not if you are trying to use proper English. Any English-class teacher worthy of the name would give you a lower mark for doing it.I think that's not true: here are some prepositional phrases at beginning of sentences.From here the road is very roughOn Friday the president will make a press statementLook at that pictureI don't know any grammar rules that govern position of prepositional phrases
He happily walked through the park.
Yes, the word happily is an adverb.An example sentence is: "I will happily drink all the tea".Another example sentence is: "the couple happily danced the night away".
the prince and princess fell in love happily ever after
I happily ran up the stairs and turned on my DS
She twirled around the room happily, enjoying the music and the company of her friends.
She happily skipped off to join her friends. The story ended happily for the trio.
There is no adjective in that sentence.
The two girls skipped happily through a field of flowers.
You can be going along quite happily, then bing; it does a U-turn.
The treasure hunters happily scooped up handfuls of gold coins from the pirate chest. The puppy bounded happily into his master's arms. And they lived happily ever after.