These words you asked are Conjunctions. Conjunctions are independent words that connect the preceding and following sentences. It is an uninflected word and is a conjunction by itself.
１．Conjunctions -Paradox : From the previous things, of course, the result opposite to the inferred result follows.
でも、（それでも): It is use to describe "unpredictable content" or "unwanted content" for a certain content mentioned above.
There are no honorifics in conjunctions. However, be careful about the conjunctions you use when writing letters and business texts. でも should not be used in polite situations
例）お腹が空いた。でも、冷蔵庫には何もない。
しかし(しかしながら）:It is used when you want to emphasize the "feeling contrasting " content that cannot be considered on the basis of the "contents mentioned above". Also, in the middle of the story, it is used to emphasize "contents that I feel are important". Written language often used in the explanatory texts and critiques. Hard words. "しかしながら" is newer and harder way to say than "しかし", and it is used when you want to emphasize the content that "feels contrasting" rather than "しかし".
例）まだ、９月の末である。しかし、今日は冬のような天気だった。
ここ最近、しばらくの間コロナウイルスで亡くなる人が少しずつ減ってきている。しかしながら、まだまだいろいろな問題点を抱えている。
が: 「しかし」is used strongly emphasize the content described later is "unexpected" and "contrast", whereas,「が」is "anticipated". It is used to lightly emphasize "contrary to" and "contrast".
例）英語は簡単だ。しかし、日本語は覚えることがたくさんある。
英語は簡単だ。が、日本語は覚えることがたくさんある。
けれども : It is used to describe things that are not usually "yes" or "yes" for a certain thing. It is also used to contrast or contrast with respect to certain things. Besides, it is used to express the speaker's opinions and feelings about the previous matter. Whereas 「しかし」puts a great deal of emphasis on what is said later than what is said earlier, 「けれど」puts some emphasis on what is said earlier, but on what is said later than before is also focused on. 「けど」「けども] i are spoken words which are simple expressions.
例）ワインはおいしい。けれども、飲みすぎもよくない。
けれど, correct word 「だけど」is also the same meaning as けれども above.
「だけど」is spoken language with intimate relationships such and friends and family.
例）うちのお母さんは普段はやさしい。だけど、怒ると怖い。
２．Conjunctions -Surprisingly-In contrast to the previous one, I will state something unexpected.
ところが It is used to state, "unexpected things" and "unexpected things" with respects to the previous
content.
例）納豆は安くて健康に良い。ところが、嫌いな人が案外多い。
３．Conjunctions-Supplementary explanation: The part that follows supplements and explains the causes and reasons of the previous things
ただ is used to lightly add "contents that you care about" and "contents that you want to keep in mind" with respect to the contents mentioned above.
ただし is used when you want to add explanations, conditions, exceptions, etc. from the objective point of view to contents mentioned above and reminds you of that. Hard way to say.
例）この器は本当に美しい。ただ、値段が少し高い。
卵は究極の完全栄養食品です。ただし、食べすぎはよくありません。
Conjunction - Old language
しかるに：It is old-fashioned expression and it may not be familiar to everyday conversation. If you like Classic or Chinese writing, you will see it relatively often.「しかるに」: Since it is a conjunction, it is used at the beginning of the second part of a series of sentences. However, it is a bit complicated in the terms of meaning, and there are 3 patterns: 1.reverse connection cases,:[However], 2 forward connection cases:[Well, By the way], and 3. simply changing the topic :[Because, that is the case], which must be judged from the context.
例）「力を尽くしたること少なからず。しかるに禄（ろく）いまだ賜らず」 「竹取物語」より
しかるに：そうであるのに、ところが
[訳] 力を尽くしたことは少しではない。ところがほうびはまだいただいていない。
There are much more information about しかるに .
I hope this is sufficient to supplement the answer to your question.
