Please show me example sentences with 如、若、像、似
Tl;dr: As an individual word in modern Chinese, they behave differently (point 1). Example sentences are discussed in point 2. Point 3 discusses their use as part of compound words or idioms.

Limiting our discussion to similes (如 and 若 can also mean 'if'; this sense is not discussed below), 像 seems to be most frequently used alone in modern Chinese (spoken and written). 如 and 似 come in second, and may appear independently in more literary contexts. 若, given its classical nature, seems to only work when as part of idioms but never alone.

Consider the following:

a. 他像一個小孩。 He is like a child.
b. 記憶像鐵軌一樣長。 Memories are as endless as the railway tracks.

It is permissible to replace 像 in the above examples with 如 or 似, but not 若. 如 or 似, however, give a more literary (somewhat old-fashioned) nuance, and must be used with caution.
Sentence a. is 'simple', where the simile forms the predicate itself (italicised). But in sentence b., the core part of the predicate (italicised) is something else (i.e. 長, long).
In that case, you may consider adding a preceding adjective/adverb (定語) before the predicate besides 像/如/似. Usual choices include 一樣, (一)般, 似的 (adjective; precedes noun only, so this is the only option that does not apply in sentence b.), and 似地 (adverb; precedes verb or adjective). Coupling like these is also possible in the simple case (e.g. sentence a.), albeit somewhat redundant.

像, 如, 似, and 若 (especially the latter three) can appear in modern Chinese as part of compound words and/or idioms.





Compounds
Idioms




像
好像
三分像人，七分像鬼


如
如同、就如、彷如、有如
如泣如訴


似
似是
驕陽似火、似水流年


若

若隱若現




Note how the idioms usually are similes themselves. They have respectable etymologies and words within should not be easily replaced. E.g., it is wrong to say *驕陽像火.