Ptolemy IV Philopator, king of Egypt 222-205 BC. See generally OCD4 p.1235, and web address 1.
[1] 'Father-loving'. (P's father was his immediate predecessor on the throne, Ptolemy III Euergetes.)
[2] The source is Polybius 5.34.10-11, which the compiler has followed almost verbatim from 'handled every part ...' to '... among whom'.
[3] Polybius 5.35.1-39.6 describes the unsuccessful plot (c.220 BCE) by Cleomenes, king of Sparta, to overthrow Ptolemy IV in Alexandria. See also Plutarch, Agis and Cleomenes 33-37.
[4] Polybius' account (at 5.40.1-3) goes straight on from Cleomenes' coup attempt to Theodotus' moves to hand Coele-Syria to Antiochus III (the Great). At 5.81.1 Polybius describes Theodotus' attempt to assassinate Ptolemy IV in his tent at night before the battle of Raphia (217 BCE).
[5] If the compiler knew any specifics to justify 'many others', he may have been thinking of Sosibius and Agathocles, Ptolemy IV's leading advisers (on whom see Polybius 15.25.1-33.12). They were probably responsible for his death in 205 BC, which they then concealed for several months (see Justin 30.2.1-8).