Navigating Option Chains on IG API

[Big_LF]

Has anyone found an better way to navigate the option chains on the IG API?

To give an example, the Hierarchy id for all US500 options is 346003 (https://api.ig.com/gateway/deal/marketnavigation/346003).
The nodes for this are option expiarys,  so far so good.  For example "DEC" currently has node id: 407780127
However the nodes for 407780127 are then (annoyingly) groups of strikes "1251-1500","1551-1600"...   ..."5501-6000"
If I want to pull the option data, I need to loop over all the strike groups (over 20 of them!), and this very quickly runs up against API usage limits.

TL:DR Is there a simpler (single call) way to get option price data for a given expiry, like it is provided from the web front end (all prices, puts and calls, by strike)?

Bonus question:  Has anyone figured out the naming convention for monthly Index Option "epic" ids?: 
(as of 25-Oct-23)
US500 DEC-23 4075 Put ==  "OP.D.SPX5.4075P.IP"
US500 MAR-24 3500 Put == "OP.D.SPX2.3500P.IP"
US500 JUN-24 2800 Put == "OP.D.SPX3.2800P.IP"

is there a convention OP.D.SPX{n}......  where n = ???