feete: metrical feet, groups of syllables forming the basic unit of the poetic meter

feet were lame: metrically defective halting; The verses (the "staff" meaning both "a line of verse" and "a crutch" and "penis) might beare (hold/sexually sustain) if the feete (male genitalia) could beare the verses (vagina; "versus" is a "furrow", the "furrow" is "the female pudendum"). However, the feet were lame (impotent)  and had no matter (semen), thus they stood lamely in the verse (i.e. "couldn't get it up" or were incompetent in the sex act)

change you colour: are you blushing?

it is a hard matter for friends to meet; but Mountains may be remoov'd with Earthquakes, and so encounter: Celia inverts the proverb, "Friends may meet, but mountains never greet"; Rosalind and Orlando have Mountains (seemingly insurmountable obstacles) dividing them so it is a hard matter for them to meet. However, Mountains may be remoov'd with earthquakes, so Rosalind can look forward to Mountains (with play on "mountings" or sexual intercourse) for she may yet encounter (make love to, with possible play on "count" and "cunt") Orlando's hard (erect) matter (penis).

petitionary vehemence: passionate pleading

out of all hooping: beyond all exclamation, "whooping"

Is he of God's making: proverbial, meaning a normal human being

head worth a hat?: is his head (penis) worth a hat (female genitalia; a hat "is a woman's privates because frequently felt")

chin worth a beard?: Rosalind hopes that his chin (jaw-line) is worth a beard (facial hair), and that his chin (penis) is worth a beard (female public hair).

little beard: Facial hair was considered a barometer of a man's virility. At age 17, Orlando might have a little beard because he's a late bloomer, but probably is because the actor who first played him had a little beard, perhaps because he had recently shaved to portray a female character. 

if the man will bee thankful: A common sentiment, if one remains grateful to God, God will bless you in return; if Orlando remains grateful to God, God may bless him with more facial hair.

stay: wait for; Rosalind is willing to stay (wait for) the growth of his beard (see above) as long as she eventually has knowledge (carnal knowledge) of his chin (penis).

divell take mocking: Rosalind is so fed up with Celia's mocking of her that she uses a very unladylike curse. She is the only woman to use the curse "the devil take" in the First Folio and this puts her in the company of such uncouth characters as Therisites, Pandarus, and Falstaff.

sadde brow, and true maid: seriously and honestly

Wherein went he?: Either, "Into which place?" or "In what condition?"

remaines: dwells

Gargantuas: a giant with a phenomenal appetite, created by French writer Rabelais in Gargantua and Pantagruel, and was also know in England from tales by other writers.

freshly: healthy

Jove's tree: The oak tree was sacred to Jupiter aka Jove.

when it droppes forth fruit: referring to the previous statement from Celia that Orlando was like an acorn dropped under the tree, Rosalind is praising this tree as one from Jove, a tree of the gods, for dropping forth such godly fruit as Orlando.

becomes: adorns

holla: whoa, stop (as to a horse)

curvettes: prances along

unseasonably: in an ill-timed manner

furnish'd: dressed

Hart: a female deer; a pun on "heart"/"Hart"

burden: continuous undersong, interruption