Marvel Chronology Project

Avengers Arena 5-FB is the origin of Anachronism and takes place before 6-FB.

Actually there are two flashbacks in Arena 5. In the first one Kid Briton gets reprimanded by Captain Britain while Elsa Bloodstone, Spitfire, Meggan & Union Jack fight a monster. That monster is shown to be Cullen Bloodstone in Arena 14.

In the second one Kid Briton bullies Aiden, who turns into Anachronism.

In Arena 6-FB Kid Briton bullies Aiden again.

It is possible that the first flashback in Arena 5 takes place after AARENA 6-FB but it is also possible those flashbacks were shown in sequence.
Option 1: AARENA 5 (11 - 13) Anachronism origin > AARENA 6-FB Anachronism confides about his transformation, gets bullied by Kid Briton > AARENA 5 (2 - 4) Kid Briton reprimanded for this
Option 2: AARENA (2 - 4) Kid Briton reprimanded for whatever & (11 - 13) > AARENA 6-FB

In any case, Cullen's presence in AARENA 5-FB needs to be added and Aiden's origin needs to be before AARENA 6-FB. Cullen, Aiden and Nara have to be corrected. Depending on whether you place the first flashback in 5 before the second flashback or after the flashback in 6, there are different corrections for Kid Briton and Union Jack.

Suggested corrections:
ANACHRONISM/AIDEN
**AARENA 5-FB move here
AARENA 6-FB
**AARENA 5-FB move from here
{AARENA 1}

NARA
AARENA 15-FB
**AARENA 5-FB move here
AARENA 6-FB
**AARENA 5-FB move from here
{AARENA 1}

Optional 1 (if you want to split the two flashbacks in issue 5):
BLOODSTONE, CULLEN
AARENA 14 (12:2 - 14:3)-FB
AARENA 6-FB
*AARENA 5-FB | cf AARENA 14
{AARENA 1}

KID BRITON
**AARENA 5 (11 - 13)-FB add here
AARENA 6-FB
**AARENA 5 (2 - 4)-FB add range
{AARENA 1}

UNION JACK III/JOEY CHAPMAN no change
ASM:ENDS
AARENA 6-FB
AARENA 5-FB
X:L2 13

Optional 2 (if you don't want to split the two flashbacks in #5 so as to keep both before #6):
BLOODSTONE, CULLEN
AARENA 14 (12:2 - 14:3)-FB
*AARENA 5-FB | cf AARENA 14
AARENA 6-FB
{AARENA 1}

KID BRITON
**AARENA 5-FB move here
AARENA 6-FB
**AARENA 5-FB move from here
{AARENA 1}

UNION JACK III/JOEY CHAPMAN
ASM:ENDS
**AARENA 5-FB move here
AARENA 6-FB
**AARENA 5-FB move from here
X:L2 13