The homophone of need is knead.
Yes, surprisingly is spelled with an S. Surprisingly is how you spell it. You spelled it correctly.
You spelled it correctly in the question.
An older word for a school principal is a headmaster or headmistress.
tense
You have spelled both correctly in your question
Yes, "negotiable" is spelled correctly.
Yes, if it is the infinitive of the verb (to choose). The past tense is spelled chose and the past participle is chosen. The verb "choose" is also a homophone of the verb conjugation "chews" (bites on).
You have spelled 'still' correctly.
Yes, engineer is spelled correctly in your question.
Flattest is spelled correctly. The others are spelled: silliest, biggest and sweetest.
Yes, surprisingly is spelled with an S. Surprisingly is how you spell it. You spelled it correctly.
You've spelled it correctly.
Would is a homophone of "wood"
The homophone of "doe" is "dough."
The homophone for strait is "straight."
The spelling "knight" is a medieval mounted or armored soldier, or the related honorary title. The homophone "night" is the period of daily darkness, as opposed to daytime.
all you have to do is type a word into Google and it will correct you if it's spelled wrong if you ever need to know. But yeah, you spelled it right